Method of and apparatus for helically coiling pipe

ABSTRACT

A system for coiling tubes for use in coiled-tube heat exchangers and especially regenerators, in which the tube is fed through a roller arrangement adapted to bend the tube into the desired radius of curvature prior to the passage of the tube onto a coiling mandrel. The roller arrangement consists of a pair of rollers spaced apart in the direction of movement of the tube and held by a steel cable onto a carriage or traveler movable along a rail parallel to the axis of the tube, and a pair of rollers, between the first two rollers, embracing the major part of the periphery of the tube and formfitting therearound such that the rollers contact the tube at three points defining the curvature. The tube is thus bent into substantially its final curvature prior to its deposition upon the mandrel.

1 Aug. 22, 1972 [54] METHOD OF AND APPARATUS FOR HELICALLY COILING PIPE [72] Inventor: Robert Funke,Tacherting,Gennany [73] Assignee: Linde Aktiengesellschaft,

Wiesboden, Germany 22 Filed: Feb.24, 1970 21 Appl.No.: 13,378

[30] Foreign Application Priority Data Feb. 27, 1969 Germany ..P 19 10 061.9

[52] US. Cl ..72/137, 72/ 144 [51] Int. Cl. ..B2lf 35/02, B2lf 3/04 [58] Field of Search ..72/137, 144, 142, 143

[56] References Cited UNITED STATES PATENTS 2,290,380 7/1942 Pierce ..72/ 144 2,179,389 11/1939 Turner ..72/138 3,482,298 12/1969 Brucker ..72/142 1,837,752 12/1931 Beneze ..72/144 FOREIGN PATENTS OR APPLICATIONS 1,294,815 4/1962 France ..72/ 142 Primary Examiner-Charles W. Lanham Assistant Examiner-R. M. Rogers Attorney-Karl F. Ross [57] ABSTRACT A system for coiling tubes for use in coiled-tube heat exchangers and especially regenerators, in which the tube is fed through a roller arrangement adapted to bend the tube into the desired radius of curvature prior to the passage of the tube onto a coiling mandrel. The roller arrangement consists of a pair of rollers spaced apart in the direction of movement of the tube and held by a steel cable onto a carriage or traveler movable along a rail parallel to the axis of the tube, and a pair of rollers, between the first two rollers, embracing the major part of the periphery of the tube and formfitting therearound such that the rollers contact the tube at three points defining the curvature. The tube is thus bent into substantially its final curvature prior to its deposition upon the mandrel.

12 Claims, 9 Drawing Figures PATENTED M1322 m2 SHEET 1 BF 4 INVENTOR ROBERT FUNKE ATTORNEY PATENTEDAus22 I972 I 3,685,330

' sum 2 or 4 ATTORNEY PA'T ENTED M1822 m2 SHEET 3 BF 4 INVENTOR R BERT FUNKE BY I marl ATTORNEY PATENTEDMJB22 m2 3,685, 330

saw u or 4 INVENTOR ROBERT FUNKE BY 9 A (KW ATTORNEY METHOD OF AND APPARATUS FOR HELICALLY COILING PIPE l. FIELD OF THE INVENTION The present invention relates to a method of and an apparatus for the coiling of tubes and, more particularly, to a system for forming helical or spiral coils of tubes for use in heat exchangers and especially regenerators.

2. BACKGROUND OF THE INVENTION The use of helical and spiral tube coils, in heat exchangers and especially regenerators in which these coils are disposed in a heat-storage mass has been proposed in various applications, including the heat exchangers described and illustrated in commonly assigned U.S. Pat. No. 3,477,496. In general, a heat exchanger embodying such tube coils may consist of a plurality of coaxial layers of tubes with intervening spacers designed to permit the passage of a fluid through the interstices of the nest or bundle and between the turns of the tubes or between the tube layers. The tubes may be bonded to the spacers or to each other by soldering or otherwise to retain the turns in the desired relationship or may be held in place under tension and/or by virtue of the tightness of the coil.

It has been proposed to provide tube coils of this type by winding the turns about a mandrel or support in a generally helical manner, the support including angularly spaced spacer elements which extend parallel to the axis of the coil. This system has, however, the disadvantage that the turns tend to extend in more or less straight-line relationship between the spacers and thus have a polygonal configuration. To avoid this disadvantage, it has also been proposed to insert a template intermittently for the bending of the coil about a substantially circular or elliptical are, thereby producing a smooth curvature over the entire turn. To this end, the tube is advanced incrementally while the template is alternately positioned for bending of the tube and withdrawn to permit advance of the bent portion of the tube. In this latter mode of operation, disadvantages arise because of the intermittent nature of the process and the time-consuming periodic interruption of the advance of the tube. In practice, the latter process has been found to be uneconomical and has not achieved widespread use.

3. OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved method of making tube coils, preferably for the purposes described, wherein the disadvantages of earlier methods can be avoided and the process can be carried out economically and substantially continuously.

It is another object of the invention to provide a continuous method of forming tube coils of helical and spiral configuration wherein the disadvantages of earlier systems are avoided and the tube coils have regular smooth bends to facilitate the uniform How of fluid through the interior of the tubes and through the interstices of the turns thereof.

A further object of the invention is the provision of an apparatus for forming tube coils which is relatively simple but free from the disadvantages of earlier systems.

4. SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, with a system for forming tube coils, especially for use in heat exchangers and, more particularly, for regenerators of the type used in low-temperature gas separation, in which a coiling mandrel is provided but, prior to passage of the tube onto the mandrel, there is a bending of the tube to impart thereto a radius of curvature corresponding substantially to the curvature of the coil; the bending is carried out in a three-point roll-type bending arrangement.

In other words, the aforementioned objects are attained by providing the tube and its individual layers, each with a uniform radius of curvature substantially continuously, i.e. without interruption of the tube feed, prior to passage of the tube onto the mandrel or other layers disposed thereon.

The system permits a high output of the coiling ap paratus as well as a rapid and economic coiling of the tubes. Because of the continuous operation of the method, uniform curvature is obtained throughout the coil with highly advantageous technological improvements in flow of the fluids through and past the coil and in thermodynamic effectiveness of the heat exchanger incorporating same. The unevenness hitherto encountered when tube coils were formed on mandrels provided with spacers in angularly spaced relationship, is thereby eliminated.

According to another feature of this invention, the bending arrangement is so constructed as to apply a uniform tension to the tube coiled upon the mandrel, thereby ensuring that the tube will always be formed with a uniform tension of the successive turns. To this end, the prebending device advantageously comprises a pair of guide rolls on one side of the tube (the upper side thereof with respect to the helix) and two coacting inclined rolls in form-fitting relationship with the tube and disposed between the two upper rolls to provide the three-point bending action mentioned earlier. The three roller units are located in series, one behind the other, upon a bar or beam support, preferably a U- shaped profile or channel. To permit adjustment of the radius of curvature of the tube, at least one of the roller units is adjustable, generally in the direction of its radius, to increase or decrease the radius of curvature of the bend, preferably via a spindle. Furthermore, means is provided to enable the coacting inclined-axis rolls to swing together and apart and thereby engage or release the tube. The latter means may include a lever or toggle arrangement as will be apparent hereinafter.

According to another feature of the invention, the rolls have contours corresponding to the contours of the tube guided therepast and thus generally concave segmental configurations when the tube is of circular profile. The invention also provides that the rolls may be replaced by corresponding contour rolls when a tube of another contour is to be employed. As a consequence, the bending arrangement may be economically used for a variety of different tube cross-sections as well as radii of curvature of the turns of the tubes of varying dimension.

To maintain a constant stretch upon the tube, according to the invention, a steel cable or wire or the like is anchored to the roller support or beam or to a carriage adapted to run along a rail parallel to the axis of the coil and mandrel. The axial movement of the carriage permits the cable to follow the turns of the tube and maintain a constant stretch or tension throughout the turns of a particular coil. To provide a constant stretch through a number of layers of coils, it is merely necessary to provide a slight adjustment of the length of the cable at the start of the winding of each new coil. Furthermore, the supply coil of the tube may be provided upon this or another rail parallel to the axis of the mandrel to permit continuous coils of relatively long tube length to be handled with economy of space.

While the invention has been generally described with respect to helical coils and is particularly suitable for use in the manufacture of such coils, it will be appreciated that an Archimedean or logarithmic spiral can also be produced in a substantially continuous manner using the apparatus and technique of the present invention. To this end, the adjusting means for setting the radius of curvature of the tube is provided with means for continuously varying the radius of curvature with advance of the tube and may be automated or automatically controlled by a conventional programming device.

5. DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a plan view, partly in diagrammatic form, of an apparatus for the formation of a helical coil in accordance with the present invention;

FIG. 2 is a side view of the system of FIG. 1, also in diagrammatic form;

FIG. 2A is a view similar to FIG. 2, illustrating another embodiment;

FIG. 3 is a detailview in side elevation of the prebending arrangement of FIG. 1;

FIG. 4 is a cross-sectional view taken generally along the line IV-IV of FIG. 3;

FIG. 5 is a cross-sectional view taken generally along the line VV of FIG. 3;

FIG. 6 is a diagram of an apparatus according to the invention for producing a spiral coil;

FIG. 7 is a view similar to FIG. 4 but showing the rollers thereof replaced by rolls of different configuration; and

FIG. 8 is a diagram illustrating the invention.

6. SPECIFIC DESCRIPTION In the apparatus illustrated in FIGS. 1 and 2, a helical coil 100 is shown to be formed by winding a metallic tube 1 (e.g. of copper) upon a mandrel 2 in the form of a drum supported at 2a and 2b by a shaft 2c and provided with spacers 4 at angularly spaced locations about the axis of rotation of the drum. A drive motor 3 rotates the drum 2 via a chain-and-sprocket arrangement 3a as illustrated in FIG. 1. The spacers 4,.which are either fixed by welding and the like or temporarily and detachably held on the surfaces of the drum 2 by magnets, clamps or other means not shown, are U- profiles or channels (see FIG. 2). They serve to space the coils from one another when the coils are used in heat exchangers as previously described or until the mounting of the coils is finished. In case it is wanted to remove the resulting tube layer from the mandrel 2 after being coiled, the spacers 4 also serve to permit the tube layer to be removed against the usual friction forces more readily than would otherwise be the case where the layer is applied directly to the mandrel.

To produce the uniform curvature of the tube 1, which may be supplied from a reel 101 as illustrated in FIG. 2A, there is provided a bending arrangement 5 which is effective before the tube is coiled upon the mandrel and which will be described in greater detail hereinafter. The principle of the bending device may be seen from FIG. 8, however, and involves the fact that three rollers 102, 103 and 104, contacting a plastically deformable elongated member 105, e.g. a tube, at points 106, 107 and 108 define a circle with a radius of curvature R, as measured from the center of curvature C to the centerline c of the tube. In the system of the present invention, the radius of curvature R corresponds to the desired radius of the coil 100.

The bending arrangement 5 is held in the same position with respect to the axis of the coil and the periphery of the drum 2 by a steel cable or wire 6 which is fixed to a carriage 7 riding a rail 8 extending parallel to the axis of the drum 6. Consequently, the same stretch is applied to the tube as it pays onto the spacers 4 of the mandrel from the bending device and a uniform curvature throughout the turns of the coil is obtained. The pitch of the helix may be controlled by regulating the angle a permitted between the plane of the cable 6 and the plane of the bending arrangement 5 or tube 1, or by providing a further guide for the tube 1 in a manner which is not material to the present invention and is well known in the art. As illustrated in FIG. 2A, upon completion of the coil 100, further spacers 109 may be positioned thereon and the further coils 110, 111, etc; formed in successive operations. In FIG. 2A, therefore, a systemis illustrated in which the successive layers 100, 110 and 111 are provided with intervening sets of spacers 109 and 112. FIG. 2A also indicates that the tube 1 may be supplied from a reel 101 rotatable on a support 1 13 forming part of the carriage 7 and guided onto reel 8. For each succeeding tube layer, it is merely necessary to increase the length of the cable 6 by the value A to maintain the desired degree of stretch and tension. The length of the cable in FIG. 2A, in which a third tube layer is shown to be coiled is thus I +2A.

In FIGS. 3 and 4, there is shown a bending arrangement of the type generally illustrated at 5 in FIGS. 1 and 2. This arrangement comprises a support beam 9 in the form of a channel or U-profile, whose web 9a and legs 9b and 9c form a structurally rigid member held in place by the cable 6. The latter can have its effective length increased by loosening the bolts 14a of a cable clamp 14b which is pivoted in a bore 14 of the support member 9. Once the effective length of the cable 6 has been increased, e.g. for the formation of successive coaxial helical coils, the bolts 14a may be tightened.

According to this invention, the support 9 canies a pair of upper rolls 10 and 11 which have a concave profile as represented at a in FIG. 5. The roll 11 is held between a pair of depending plates one of which is shown at 1 la and is mounted upon a pin 11b which like the pin 10b supporting the roll 10, is removable to permit replacement of the rolls 10 and 11 by rolls of another contour to accommodate tubes of a different configuration. It has been found to be convenient to mount the adjustable roll 10 in a radially shiftable support 22 slidable in a guide sleeve 25 inclined at an angle B of 70 to 75. A spindle 21 has a polygonal head 21a engageable by an appropriate wrench or hand wheel and is threadedly received in a nut 25a at the upper end of the sleeve 25 while being locked at 21b to the upper end of the body 22. A combined thrust and journal bearing 22a is fixed in a plate 22b at the top of the body 22. Hence, upon rotation of the spindle 21, the body 22 will be shifted radially (arrow to increase or decrease the radius of curvature R of the system.

Between the rollers 10 and 11, there is provided a pair of inclined-axis rolls 12 and 13 which embrace the tube 1 substantially all around the latter and at least from below and the sides thereof. When reference is made to inclined axis herein, it is intended thereby to refer to rolls whose axis 12b and 13b lie at an angle to the plane P of the prebending assembly and the tube 1 processed thereby. In the embodiment illustrated, the axes 12b and 13b include angles y of about 45 with the plane P and an angle 2 'y with one another in the closed position of these co-operating rolls.

The rolls 12 and 13 are here shown to be mounted upon respective shafts 12c and 13c by respective locking nuts 12d and 13d which are removable to enable the rolls to be replaced by rolls l2 and 13 (FIG. 7), for example, whose profiles 12d and 13d are different to accommodate a tube 1' of different configuration. In FIG. 7, for example, the tube is shown to be of square cross-section or profile so that the profiles 12d and 13d are likewise right-angled. In the arrangement illustrated in FIG. 4, in which the tube 1 is shown to have a circular profile, the profiles 12s and 13e are shown to be arcuately concave and to extend at least through one quadrant each of an arch and close to 180 of the circumference of the tube. An all-around embrace of the tube or pipe 1 is thus definable as an enclosing of the tube such that it cannot escape in any transverse direction.

The shafts 12c and 13c are in turn carried by levers 12f and 13f which are pivotally connected at 115 in a tongs junction so that an outward movement of the shafts as represented by arrows 12a and 13a can be effected by an inwardly swing of the upper ends of the levers 12f and 13f. The pivot 115 is held, in turn, between a pair of plates 116 depending from the support 9.

At their upper ends, the levers 12f and 13f are recessed at 12g and 13g to accommodate compression springs 18 and 19 respectively, which urge the lever 12f in the counterclockwise sense and the lever 13f in the clockwise sense. A wedge 17 has its shank 17b guided in a sleeve 170 of the support 9 and a point 17d receivable between ramp surfaces 12h and 13h of the levers 12f and 13f to hold the rolls l2 and 13 in their forming position around the tube 1.

The wedge 17 is, in turn, vertically displaceable by a lever 15 to release the tube. The lever 15 is pivoted at 15b upon the support 9 and carries a camming roller 15c riding upon a further lever 16. In the solid-line position of the lever 15, the roller 15c engages a horizontal stretch 16a of the cam surface 16b to lock the rolls 12 and 13 closed. The lever 16, in turn, is fulcrumed at 16c to the support 9, i.e. at a location between upwardly extending finger 16d and the horizontal surface 16a so that, when the lever 15 is swung in the clockwise sense (dot-dash-line position in FIG. 3), the roll 15c engages the finger 16d and swings the lever 16 in the clockwise sense to lift the wedge 17 in the direction of arrow 17a. To this end, the wedge 17 carries a pin 17e which is slidable in a slot 16e of the lever 16. When the wedge 17 is lifted, therefore, the rolls 12 and 13 swing outwardly to clear the tube 1 and permit its removal in the direction of the arrow 1b.

In FIG. 3, the mounting of the sleeve 25 upon the support 9 is also shown in detail. A plate 23 is welded to the channel 9 at the aforementioned angle [3 while a plate 24 carried by the sleeve is boltedto the plate 23.

In FIG. 6, there is diagrammatically illustrated an arrangement whereby the bending device 5 can also be used to form a spiral coil 200. In this arrangement, the spacers 204 are provided between successive turns of the coil which is formed upon a mandrel 202 driven by a motor 203. In this case, however, the spindle 225 of the leading roll 210 of the device 5 is withdrawn by a servomotor 250 in step with the feed of the tube and rotation of the mandrel 202 to progressively increase the radius of curvature. To maintain a constant stretch, the cable 6 can be paid out from a reel 251 via a servomotor 252 under the control of a progresser 253.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

Iclaim:

1. A method of forming a'tube coil comprising the steps of:

depositing successive turns of a plastically deformable tube upon a mandrel while continuously rotating same and feeding the tube thereto;

bending the tubing continuously prior to its deposition upon the mandrel by continuously feeding the tubing through a three-point bending arrangement defining the radius of bend curvature corresponding to the curvature of the coil formed on the mandrel; and

maintaining a constant tension upon said tubing as it is wound upon said mandrel, said coil being formed generally helically upon said mandrel, said tension being maintained by holding said threepoint arrangement with a cable and permitting said cable to shift parallel to the axis of said mandrel with the deposition of successive turns thereon.

2. The method defined in claim 1 wherein said coil is generally a helix, further comprising the step of paying out said tube to said three-point arrangement from a supply roll shiftable parallel to the axis of the helix during the deposition of successive turns thereon.

3. An apparatus for coiling tubing, comprising a rotatable mandrel; bending means for depositing successive tubing turns on said mandrel, said bending means including:

a support movable relative to said mandrel,

a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof,

a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers and journaled on said support, said first and second rollers together defining a bending are having a radius of curvature corresponding substantially to that of the coil formed on said mandrel; and

means connected with said arrangement for maintaining a predetermined constant tension in said tubing during the deposition thereof on said mandrel.

4. The device defined in claim 3, further comprising means on said support for displacing one of said rollers relatively thereto for varying said radius of curvature.

5. The apparatus defined in claim 4 wherein the lastmentioned means is a threaded spindle coupled with one of said first rollers.

6. The apparatus defined in claim 4 wherein said second rollers have a profile corresponding substantially to the profile of said tube, further comprising means for replacing said second rollers to vary the configuration of the tube bent in said apparatus.

7. An apparatus for coiling tubing, comprising a rotatable mandrel; and bending means for depositing successive tubing turns on said mandrel, said bending means including a support movable relative to said mandrel,

a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof,

a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers andjournaled on said support, said first and second rollers together defining a bending arc having a radius of curvature corresponding substantially to that of the coil formed on said mandrel, and

lever means for swinging said second rollers toward and away from one another to engage and release said tube respectively.

8. The apparatus defined in claim 7 wherein said support includes a channeled beam and said mandrel includes a drum provided with angularly offset spacers therearound, said apparatus further comprising:

a rail extending alongside said mandrel and parallel to the axis thereof;

a carriage shiftable on said rail parallel to the axis of said mandrel; and

an elongated member of adjustable effective length anchored to said carriage and said beam for maintaining a predetermined tension of the tube wound on said mandrel, said beam being formed with guide means for one of said first rollers;

a threaded spindle operatively connected to said guide means for displacing said oneof said first rollers to adjust said radius of curvature;

a pair of pivotally connected levers each rotatably journaling one of said second rollers with the axis thereof inclined to one another and to the plane of said beam, spring means co-operating with said levers for urging said second rollers out of embracing relationship with said tube;

wedge means on said support engageable with said levers for driving same against said spring means and swinging said second rollers into embracing 9. Thedevice defined in claim 7, further comprising means on said support for displacing one of said rollers relatively thereto for varying said radius of curvature.

10. The apparatus defined in claim 9 wherein the last-mentioned means is a threaded spindle coupled with one of said first rollers.

11. The apparatus defined in claim 9 wherein said second rollers have a profile corresponding substantially to the profile of said tube, further comprising means for replacing said second rollers to vary the configuration of the tube bent in said apparatus.

12. An apparatus for coiling tubing, comprising a rotatable mandrel; and bending means for depositing successive tubing turns on said mandrel, said bending means including:

a support movable relative to said mandrel,

a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof,

a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers and joumaled on said support, said first and second rollers together defining a bending are having a radius of curvature corresponding substantially to that of the coil formed on said mandrel, said support including a channeled beam and said mandrel including a drum provided with an gularly offset spacers therearound;

a rail extending alongside said mandrel and parallel to the axis thereof;

a carriage shiftable on said rail parallel to the axis of said mandrel; and

an elongated member of adjustable effective length anchored to said carriage and said beam for maintaining a predetermined tension of the tube wound on said mandrel, said beam being formed with guide means for one of said first rollers,

a threaded spindle operatively connected to said guide means for displacing said one of said first rollers to adjust said radius of curvature,

a pair of pivotally connected levers each rotatably journaling one of said second rollers with the axis thereof inclined to one another and to the plane of said beam, spring means co-operating with said leversfor urging said second rollers out of embracing relationship with said tube,

wedge means on said support engageable with said levers for driving same against said spring means and swinging said second rollers into embracing relationship with said tube, and

mechanism for shifting said wedge means. 

1. A method of forming a tube coil comprising the steps of: depositing successive turns of a plastically deformable tube upon a mandrel while continuously rotating same and feeding the tube thereto; bending the tubing continuously prior to its deposition upon the mandrel by continuously feeding the tubing through a threepoint bending arrangement defining the radius of bend curvature corresponding to the curvature of the coil formed on the mandrel; and maintaining a constant tension upon said tubing as it is wound upon said mandrel, said coil being formed generally helically upon said mandrel, said tension being maintained by holding said three-point arrangement with a cable and permitting said cable to shift parallel to the axis of said mandrel with the deposition of successive turns thereon.
 2. The method defined in claim 1 wherein said coil is generally a helix, further comprising the step of paying out said tube to said three-point arrangement from a supply roll shiftable parallel to the axis of the helix during the deposition of successive turns thereon.
 3. An apparatus for coiling tubing, comprising a rotatable mandrel; bending means for depositing successive tubing turns on said mandrel, said bending means including: a support movable relative to said mandrel, a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof, a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers and journaled on said support, said first and second rollers together defining a bending arc having a radius of curvature corresponding substantially to that of the coil formed on said mandrel; and means connected with said arrangement for maintaining a predetermined constant tension in said tubing during the deposition thereof on said mandrel.
 4. The device defined in claim 3, further comprising means on said support for displacing one of said rollers relatively thereto for varying said radius of curvature.
 5. The apparatus defined in claim 4 wherein the last-mentioned means is a threaded spindle coupled with one of said first rollers.
 6. The apparatus defined in claim 4 wherein said second rollers have a profile corresponding substantially to the profile of said tube, further comprising means for replacing said second rollers to vary the configuration of the tube bent in said apparatus.
 7. An apparatus for coiling tubing, comprising a rotatable mandrel; and bending means for depositing successive tubing turns on said mandrel, said bending means including a support movable relative to said mandrel, a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof, a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers and journaled on said support, said first and second rollers together defining a bending arc having a radius of curvature corresponding substantially to that of the coil formed on said mandrel, and lever means for swinging said second rollers toward and away from one another to engage and release said tube respectively.
 8. The apparatus defined in claim 7 wherein said support includes a channeled beam and said mandrel includes a drum provided with angularly offset spacers therearound, said apparatus further comprising: a rail extending alongside said mandrel and parallel to the axis thereof; a carriage shiftable on said rail parallel to the axis of said mandrel; and an elongated member of adjustable effective length anchored to said carriage and said beam for maintaining a predetermined tension of the tube wound on said mandrel, said bEam being formed with guide means for one of said first rollers; a threaded spindle operatively connected to said guide means for displacing said one of said first rollers to adjust said radius of curvature; a pair of pivotally connected levers each rotatably journaling one of said second rollers with the axis thereof inclined to one another and to the plane of said beam, spring means co-operating with said levers for urging said second rollers out of embracing relationship with said tube; wedge means on said support engageable with said levers for driving same against said spring means and swinging said second rollers into embracing relationship with said tube, and mechanism for shifting said wedge means.
 9. The device defined in claim 7, further comprising means on said support for displacing one of said rollers relatively thereto for varying said radius of curvature.
 10. The apparatus defined in claim 9 wherein the last-mentioned means is a threaded spindle coupled with one of said first rollers.
 11. The apparatus defined in claim 9 wherein said second rollers have a profile corresponding substantially to the profile of said tube, further comprising means for replacing said second rollers to vary the configuration of the tube bent in said apparatus.
 12. An apparatus for coiling tubing, comprising a rotatable mandrel; and bending means for depositing successive tubing turns on said mandrel, said bending means including: a support movable relative to said mandrel, a pair of first rollers spaced apart along said support and engaging the tubing along one side thereof, a pair of co-operating second rollers in substantially all-around embrace with said tubing between said first rollers and journaled on said support, said first and second rollers together defining a bending arc having a radius of curvature corresponding substantially to that of the coil formed on said mandrel, said support including a channeled beam and said mandrel including a drum provided with angularly offset spacers therearound; a rail extending alongside said mandrel and parallel to the axis thereof; a carriage shiftable on said rail parallel to the axis of said mandrel; and an elongated member of adjustable effective length anchored to said carriage and said beam for maintaining a predetermined tension of the tube wound on said mandrel, said beam being formed with guide means for one of said first rollers, a threaded spindle operatively connected to said guide means for displacing said one of said first rollers to adjust said radius of curvature, a pair of pivotally connected levers each rotatably journaling one of said second rollers with the axis thereof inclined to one another and to the plane of said beam, spring means co-operating with said levers for urging said second rollers out of embracing relationship with said tube, wedge means on said support engageable with said levers for driving same against said spring means and swinging said second rollers into embracing relationship with said tube, and mechanism for shifting said wedge means. 